re:  I am still trying to locate a break fluid leak under the dash of
my 84 Vanagon.

Mine (both master cylinders) only leaked in cold weather, leading me
to believe something shrinks or contracts.  Just leaked while standing
overnight, never when operating the cylinder that I'm aware of.  Went
a whole summer between leaking spells with no problems.  Luckily my
'81 has rubber floormats, no carpet anywhere.  The master cylinders
are really the only things that could be leaking, as failed lines or
connections seem unlikely.